This invention relates to operation control apparatus in a combustion device such as a gas water heater having an electric member such as an electromagnetic safety valve or an ignition plug.
There has been hitherto known operation control apparatus, in a combustion device, comprising (a) an operation member which is movable to be changed over between a starting end stop position, an intermediate open position, and a final end ignition position; (b) an electric member comprising for example an electromagnetic safety valve which is to be energized for operation and be continued in operation even after the operation member is returned to the intermediate open position; and (c) a limited time operation circuit for operating the electromagnetic safety valve so that if the operation member is moved from the stop position through the open position to the ignition position, the limited time operation circuit starts to run and burner ignition can take place. Thereby the electromagnetic safety valve is kept in its open condition by the continuing operation of the limited time operation circuit for a predetermined period from the time when the operation member is returned to the open position, to the time when a predetermined electromotive force is generated from a thermo-couple heated by the ignited burner and thereby the electromagnetic safety valve is kept in its open condition. There is an inconvenience, however, in that the limited time operation circuit is started in operation before ignition actually occurs, and consequently if there remains a large amount of air in a gas supply pipe at the time of attempted ignition of the burner, there is the possibility that, before air purging is completely effected and the burner can be ignited, the limited time operation circuit will have run its set time and ceased its operation, so that the electromagnetic safety valve is closed.
According to the present invention, there is provided an operation control apparatus, in a combination device, comprising an operation member selectively settable at a stop position, an ignition position or an open position; an electric member which is energised by an electric power source when the operation member is set in its ignition position; and a limited time operation circuit for affecting the operation of the electric member, either by itself energising the electric member or by enabling the electric member to be energised by the power source, for a predetermined period of time, the limited time operation circuit being inoperative for affecting the operation of the electric member while the operation member is set in its ignition position and the electric member is energised by the power source, and commencing to affect the operation of the electric member and thereafter continuing so to do for a set period of time upon subsequent setting of the operation member in its open position. Since it is so arranged that (a) when the operation member is at the ignition position, the electric member (such as an electromagnetic safety valve) is directly energised for operation by the electric power source and the limited time operation circuit is restrained from running, and (b) it is when the operation member is returned to the open position that the limited time operation circuit is started to run, it is only at the time of return movement of the operation member to the open position that the electric member commences to be held in its energised state by, or as a result of the effect of, the operation circuit and therefore it is from this moment that the electric member is operated reliably for a predetermined period of time. In this way a longer period is obtained for effecting air purging as compared with conventional apparatus in which the operation circuit commences to run at an earlier stage. This is achieved without including a purge time necessary for obtaining air purging in the set period of time of the operation circuit, as required in the conventional apparatus, so that the set period of time of the operation circuit can be shortened as compared with the conventional apparatus.